Traditional surgical procedures for pathologies located deep within the body can cause significant trauma to the intervening tissues. These open procedures often require a long incision, extensive muscle stripping, prolonged retraction of tissues, denervation and devascularization of tissue. Most of these surgeries require a recovery room time of several hours and several weeks of post-operative recovery time due to the use of general anesthesia and the destruction of tissue during the surgical procedure. In some cases, these invasive procedures lead to permanent scarring and pain that can be more severe than the pain leading to the surgical intervention.
In a typical open procedure, tissue retractors are used to maintain the working space and provide clearance for various instruments, tools and implants. Typically, several tissue retractors are used to retract skin and muscle layers, as well as vascular and neural structures that may otherwise infringe on the working space. In spinal surgery, exposure of the affected vertebral level, such as for a discectomy and implantation of a fusion cage, can be very involved and can require a complicated array of tissue retractors to maintain the working space.
A common open procedure for disc herniation, laminectomy followed by discectomy, requires stripping or dissection of the major muscles of the back to expose the spine. In a posterior approach, tissue including spinal nerves and blood vessels around the dural sac, ligaments and muscle must be retracted to clear a channel from the skin to the disc. These procedures normally take at least one-two hours to perform under general anesthesia and require post-operative recovery periods of two weeks. In addition to the long recovery time, the destruction of tissue is a major disadvantage of open spinal procedures. This aspect of open procedures is even more invasive when the discectomy is accompanies by fusion of the adjacent vertebrae. Many patients are reluctant to seek surgery as a solution to pain caused by herniated discs and other spinal conditions because of the severe pain sometimes associated with the muscle dissection.
Minimally invasive alternatives, such as arthroscopic or endoscopic techniques, can reduce pain, post-operative recovery time and the destruction of healthy tissue. Orthopedic surgical patients have particularly benefitted from minimally invasive surgical techniques. The site of a pathology is accessed through portals rather than through a significant incision thus preserving the integrity of the intervening tissues. These minimally invasive techniques also often require only local anesthesia. The avoidance of general anesthesia reduces post-operative recovery time and the risk of complications. Minimally invasive surgical techniques are particularly desirable for spinal and neurosurgical applications because of the need for access to locations deep within the body and the range of damage to vital intervening tissues.
In order to further reduce the post-operative recovery time and pain associated with spinal and other procedures, micro-surgical techniques have been developed. For example, in micro-surgical discectomies, the disc is accessed by cutting a channel from the surface of the patient's back to the disc through a small incision. An operating microscope or loupes is used to visualize the surgical field. Small diameter micro-surgical instruments are passed through the small incision and between two laminae and into the disc. The intervening tissues are disrupted less because the incision is smaller. Although these micro-surgical procedures are less invasive, they still involve some of the same complications associated with open procedures, such as injury to the nerve root and dural sac, perineural scar formation, reherniation at the surgical site and instability due to excess bone removal.
The development of systems for performing percutaneous spinal procedures has yielded a major improvement in reducing recovery time and post-operative pain because they require minimal, if any, muscle dissection, and they can be performed under local anesthesia. One such newly developed system is the MED.TM. Micro Endoscopic Discectomy System manufactured and sold by Sofamor Danek Co., Inc. of Memphis, Tenn. The MED.TM. System includes a large working channel cannula that is disposed percutaneously so that its distal end is at the surgical site. The large working channel permits the introduction of multiple surgical instruments, including an endoscope to permit direct visualization of the surgical site. As with most percutaneous or endoscopic systems, the MED.TM. System relies upon indirect visualization techniques, such as lateral fluoroscopy, to orient the large working channel cannula. In addition, like other percutaneous techniques, the MED.TM. System is inserted into the patient through a small incision.
In recent years, laparoscopic surgery has been employed to treat various anterior pathologies. However, these particular procedures are very difficult to learn and often require the assistance of a general surgeon. In addition, they often result in an increase of operative time because of the difficulty of these techniques.
Although the MED.TM. System has taken a great step toward advancing the field of percutaneous or endoscopic systems and techniques, it is not the answer for all surgical procedures or for all surgeons. For example, many surgeons have difficulty mastering the techniques associated with percutaneous surgical instruments. In addition, certain surgical procedures require a larger working space than many percutaneous systems can accommodate.
Consequently, there is a need for a system and associated techniques that combine the beneficial aspects of both open surgical techniques and percutaneous surgical techniques. There is a further need for a surgical system that can be readily and easily mastered by all surgeons of various skill levels.